Dyeing of acrylonitrile polymers using acetate dyes and m-cresol as an assistant



Patented June 27, 1950 ONITRILE POLYMERS DYEING OF ACRYL USING ACETATE AN ASSISTANT DYES AND M-CRESOL AS John Cadwallader Richards, Urbana, Ill., assignor to E. I. du Pont de Nemours & Company, Wilmington; Del., a

corporation of Delaware No Drawing. Application August 29, 1947, Serial No. 771,381

'7 Claims. (01. 8-4) This invention relates to the modification of polymers of acrylonitrlle. More particularly,- it relates to the dyeing of structures comprising acrylonitrile polymers.

By structures" is meant shaped articles, such as yarns, films, bristles, fabrics, tubings, molded articles and the like, and by acrylonitrile polymers is meant those polymers containing at least 85% by weight of acrylonitrile.

Alcrylonitrile polymers containing a major portion of acrylonitrlle are relatively insoluble, unreactive and hydrophobic materials. These characteristics make the dyeing of structures prepared from such polymers a dlfllk'lllll] problem. indeed, standard commercial dyeing techhiques can not be used satisfactorily. For example, only light shades are obtained on dyeing structures of polyacrylonitrile with acetate, basic and c rtain vat colors. This is true for copolymore of acrylonitrile which show only a slightly enhanced dye receptivity. Since the physical and chemical properties of shaped articles prepared from acrylonitrile polymers make the articles of considerable commercial interest, solutions to the dificult dyeing problems are highly desirable.

Accordingly, it is an object of this invention to provide a satisfactory process for dyeing structures prepared from acrylonitrile polymers. A further object is the provision of methods for uniformly dyeing structures of acrylonitrile polymers. A still further object is the provision oi dyed structures of such polymers which are deeply and uniformly dyed and which are fast to light and to washing. Other objects will appear hereinafter.

The objects of this invention are accomplished by treating the structures of this invention with an aqueous dye bath containing 1% to by weight of the bath, of meta-cresol and a dispersed acetate of basic dye.

The invention will be more clearly understood by referring to the examples and discussion which follow. These examples are given for illustrative purposes and are not to be com strued in any sense as limitative. Parts, proportions and percentages are by weight unless otherwise indicated.

EXAMPLE I A dye bath was prepared using 5000 parts of water, 5 parts of 1,4,5,8-tetra-aminoanthraquinone and parts of meta-cresol. 100 parts of polyacrylonitrile yarn was immersed in the bath. The immersion time was one hour and the bath temperature was 95 C. The yarn was then added to 10,000 parts of water rinsed in water, scoured in 0.5% soap solution and finally dried. The yarn was dyed a strong shade of blue. Upon examination of cross-sections of the dyed yam it was found that the dye penetrated the fiber completely. In comparison, similar yarn treated with a control dye bath, that is, one containing no meta-cresol, was colored only to a very light shade.

EXAMLPLE II To a dye bath containing 2000 parts of water, 5 parts of l-hydroxy l-aminoanthraquinone and parts of meta-=cresol and heated to 95 6. was added 100 parts of a fabric prepared from a Sil /l0 copolymer of acrylonitrile and methacrylic acid. The fabric was allowed to remain in the bath for one hour. After rinsing, scouring and drying, the fabric retained a deep shade of in comparison, a similar dye bath containing no meta-cresol had very little coloring efi'ect on. another sample of the fabric.

10 parts of the dye p-nitroaniline anlline was containing 50c bath so formed parts of meta-cresol. The dye was heated to C. and 100 parts of a polyacrylonitrile knit tubing was immersed in the bath for one hour. After purification the knit tubing was colored a deep orange. The dyed product was fast to washing and cracking.

EXAWLE "IV A film was prepared from a 90/10 copolymer mof acrylonitrile/acrylic acid using the usual casting technique. l00 parts of this film was dyed by immersion for one hour at C'. in a dye bath containing 5000 parts of water, 5 parts of a. basic dyestufi, namely, fuchsin, and 50 parts of meta-cresol. After purification, the film was found to be thoroughly dyed to a strong red shade.

EXAMPLE V A dye bath was prepared using 5 parts of malachite green, 2000 parts of water and 60 parts of meta-cresol. parts of :9. flat fabric prepared from polyacrylonitrile yarn was kept in the bath for one hour, thebath being at a temperature of 95 C. The fabric was then rinsed, scoured and dried in the usual manner. A good strong, green shade was obtained. Like the other dyed structures, this had very good resistance to washing, crocking and wear by hurling or scratching.

EXAMPLE V11 To determine the effect of varying the amount of meta-cresol, unit weight samples of polyacrylonitrlle yarns were dyed at 95 C. to 100 C. in baths containing 10%, based on the weight of yarn, of l,4,5,8-tetra-aminoanthraquinone using a 50:1 bath to yarn ratio. The baths contained various amounts of meta-cresol. The dyed samples were rinsed free of surface color, were then dissolved in dimethyl formamide and the resultant solutions were analyzed spectrophotometrically for dye content. The results are given in Table I.

Table I m Relative sample g'ge Dye Content l 2 3. 7 3 4. 5 5 ca. 2.8

, From the above figures it can be seen that the deepest shades are obtained using about 3% of meta-cresol. Use of baths containing 5% or more meta-cresol resulted in lighter dyeing than that obtained with 2% metal-cresol. The dyeing obtained using from 1% to 5%, based on the bath, is satisfactory and while lower and higher amounts can be used, this is the preferred range. Standard commercial dyeing processes usually employ 30:1 to 50:1 ratios of bath to fabric and these ratios may be used in this invention.

Other phenolic compounds can be used as assistants in the dyeing of acrylonitrile polymer structures with dispersed acetate and basic colors. For example, phenol, ortho-cresol, para-cresol and homologues of these various phenols may be employed in the process of this invention. However, meta-cresol is by far the most effective of the phenolic compounds. For example, while 'ioeta-naphthol in 0.5% concentrations is equivalent to 2% phenol, beta-naphthol is not a satisfactory assistant. Its insolubility results in its crystallizing out of the dye bath and makes its removal from the dyed structures difficult. Further, it exerts a serious, deleterious efiect on the light fastness of the dyeings. Meta-cresol has none of these faults and in addition, has the advantage that it is very effective. It is preferred to phenol, beta-naphthol, p-phenylphenol and other phenols which either do not as effectively assist the dyeing or exert adverse effects on the dyeings. The reason for the outstanding effectiveness of meta-cresol over the other phenolic materials is not known. Since only light shades are obtained with phenolic materials other than meta-cresol, it is preferred for commercial purposes to use meta-cresol for the dyeing of structures prepared from acrylonitrile polymers.

The rate of dyeing depends to some extent upon the temperature of the bath. At temperatures below C. the rate of dyeing is too slow to be practical. Accordingly, it is preferred to carry out the dyeings in accordance with the process of this invention at a temperature above 85 C. The use of higher temperatures such as C. and above leads to faster dyeing rates. Usually the dyeing will be effected at the boiling temperature of the bath. Temperatures above the boiling point may be used but since these require the use of relatively complicated apparatus they will not be used for the most part.

The dyeing may be carried out in any conventional manner using any dye, in any desired amount, selected from a number of classes such as dispersed acetate and basic dyestuffs. For example, the following dyes may be used in this invention: p-nitroaniline aniline, 4-aminoazobenzene, 4,4'-diaminoazobenzene, l,4,5,8- tetraaminoanthraquinone, l-amino-Z-methylanthraquinone, 1 hydroxy 4 aminoanthraquinone, fuchsin, malachite green, -aminoacetanilide-A- chlorophenol, 4-aminoacetophenoneaniline, and methyl violet may be added to the dyebath beside those indicated in the above examples. Further, the purification techniques may be varied to suit the objective desired. In general, conventional dyeing apparatus and procedures, such as purification methods may be used herein.

The acrylonitrile polymers which are generally used commercially to form the shaped articles described in this invention are those having a sufliciently high molecular weight to possess filmor filament-forming properties. The polymers employed possess an average molecular weight within the range of 25,000 to 750,000 or even higher, and preferably between the range of 40,000 and 250,000 as calculated from viscosity measurements by the Staudinger equation.

Molecular weight= wherein:

K,,,=l.5X 10- N ,,=speciiic viscosity and C=concentration of the solution expressed as the number of moles of the monomer (calculated) per liter of solution.

It is to be understood, however, that acrylonitrile polymers having molecular weights below or above the range indicated may be dyed by the process of this invention.

The acrylonitrile polymers of commercial interest are those containing at least 85%, by weight of the polymer, of acrylonitrile. These polymers include polyacrylonitrile and copolymers and interpolymers of acrylonitrile with other polymerizable monomers. These monomers include, among others, vinyl acetate, vinyl chloride, acrylic and methacrylic acids or derivatives and homologues thereof, styrene, methyl vinyl ketone, and isobutylene or other similar polymerizable hydrocarbons. Polymers containing less than 85% of acrylonitrile can usually be dyed by the standard processes, since inclusion of greater amounts of such materials as acrylic acid, methyl vinyl ketone and the like leads to better dye receptivity. If desired, the process of this invention can be used to dye such polymers. However, since it is preferred to uspolymers having at least 85% of acrylonitrile to get the benefit of superior properties, such as toughness and chemical inertness, the process of this invention is chiefly of interest in the dyeing of structures prepared from polymers containing a major portion of acrylonitrlle.

The yarns described herein-are prepared by conventional wet or dry spinning techniques from solutions of polyacrylonitrlle or copolymers con taining 85% or more acryonitrile in dimethyl formamide, tetramethylene sulfone or other known volatile solvents for these polymers, such as those described in Patents U. S. 2,404,714 to 2,404,727, inclusive. On leaving the spinning cell, the yarn is collected in a suitable package and this yarn package may then be washed free of residual solvent. In order to obtain full benefit of the properties of these yarns, it is desirable to draw the yarn from 2 to times its original length. Moreover, when heated under tension for extended periods of time, the yarns show a remarkable retention of tenacity; while, on the other hand, if the yarns after drawing are heated in the relaxed state at temperatures in the order of 130 to 200 0., they tend to shrink somewhat and such an after-treatment can be used to increase the elongation of the yarn to a point where they are satisfactory for use in the textile art.

Any of the structures, such as yarns, films,

fabrics and the like, may be prepared by the 1 usual techniques. For example, yarns and fibers may be prepared by dry or wet spinning, as described for example, in copending applications Serial Nos. 496,376, 735,666 or 746,651, now re spectively U. S. Patents 2,426,719, 2,451,420 and 2,467,553. Films may be prepared in similar ways, or by casting techniques. Fabrics may be prepared by any of the weil-known knitting or weaving techniques.

Normally, structures prepared from acrylonitrile polymers can not be dyed satisfactorily with any dye, such as acid, direct, sulfur, acetate, basic or vat colors. At best only light shades are obtained with acetate, basic and certain vat dyes in standard processes. By the process of this invention, it is possible to obtain satisfactory dyeing with dispersed acetate and basic dyes. Further, as disclosed in copending application Serial No. 771,243, m-cresol can be used effectively as an assistant in the dyeing of blends of 'acrylonitrile polymers and polyvinyl pyridines with acid and direct colors. I

The effectiveness of meta-cresol is surprising. While the solubility of the assistant in the polymer is important, this is only one factor. For example, other phenolic materials, such as phenol, which have solubility characteristics similar to meta-cresol are relatively ineffective in the process of this invention when compared to meta-cresol. The best dye assistant for a particular synthetic fiber is not always the most eficient assistant for all classes of dye stuffs on that same fiber. Nor can it be predicted that an assistant effective in the dyeing of one class of synthetic structures will be efiective in the dye ing of other classes of synthetic structures. For example, assistants efiective in the dyeing of polymers of vinyl chloride containing chiefly vinyl chloride or assistants effective in the dyeing of other polymers, such as the phenolaldehyde resins, are not necessarily effective in the dyeing of acrylonitrile polymers. It is impossible to predict which class and in turn which memher of a class of so called dye assistants will be most effective for a new synthetic fiber. Thus, aromatic amine carriers, such as aniline, which are eifective assistants in the vat dyeing of structures of acrylonitrile polymers as described in copending application Serial No. 771,379, are unsatisfactory as assistants in the dyeing of the structures with acetate colors because they cause a very noticeable, uncontrolled darkening of the structures. On the other hand, m-cresol, which, as described herein, is an exceedingly effective assistant with dispersed acetate or basic dyes, does not satisfactorily assist the vat dyeing of the structures. The relative insoluble and unreactive character of acrylonitrile polymers makes the dyeing of structures prepared from such polymers exceedingly diilicult.

This invention provides a convenient and valuable method for dyeing structures prepared from acrylonitrile polymers. By the novel process of this invention diiiiculty dyed structures of acrylonitrile polymers can be dyed readily at a rapid rate using standard commercial equipment. The dye bath exhaust is greatly increased and the colored products produced are dyed to deeper shades than hitherto obtainable. Further, the dyed products have exceptionally good resistance to washing and crocking. The structures are colored throughout and have excellent resistance to wear by scratching or scuiiing. Furthermore, the physical and chemical properties of the dyed structures are comparable to the desired properties of the undyed structures.

Any departure from the above description which coniorms to the present invention is intended to be included within the scope of the claims.

I claim:

1. A process for dyeing structures prepared from acrylonitrile polymers which comprises treating said structures with an aqueous dye hath containing 3% to 5% by weight of the bath of meta-cresol and a dispersed acetate dye.

2. A process for dyeing structures prepared from acrylonitrile polymers which comprises treating said structures at a temperature above C. with an aqueous dye bath containing 1% to 5% based on the weight of the bath of metacresol and a dispersed acetate dye.

3. A process for dyeing structures prepared from polyacrylonitrile which comprises treating said structures with an aqueous dye bath containing 1% to 5% based on the weight of the bath of ineta-cresol and a dispersed acetate dye.

i. A process for dyeing structures prepared from an acrylonitrile/methacrylic acid polymer containing at least 85% acrylonitrile which comprises treating said structures with an aqueous dye bath containing 1% to 5% based on the weight of the bath of meta-cresol and a dispersed acetate dye.

5. A process for dyeing structures prepared from an acrylonitrile/styrene polymer containing at least 85% of acryiontrile which comprises treating said structures with an aqueous dye bath containing 1% to 5% based on the weight of the bath of meta-cresol and a dispersed acetate dye.

6. A process for dyeing structures prepared from acrylonitrile polymers which comprises in;- mersing said structures in an aqueous dye bath containing 1,4,5,8-tetraaminoanthraquihone and 1% to 5%, based on the weight of the bath, of ineta-cresol, the said bath being heated to a temperature of from 85 C. to C.

7. A process in accordance with claim which the said structures are yarns prepared Nmhber Name Date from ".?3'1?Z&mm RICHARDS I m 2,431,956 Moody Dec. 2, 1947 REFERENCES CITED 5 OTHER REFERENCES The following references are of record in the Dyeing of Vmyon by J. A. Woodrum pagw file of this patent: 194-197, 204, 205 of Amer. Dyes. Reporter for UNITED STATES PATENTS Apr. 22, 1946.

Number! Name Date 2347 508 Rugeley Apr. 25, 1944 

1. A PROCESS FOR DYEING STRUCTURES PREPARED FROM ACRYLONITRILE POLYMERS WHICH COMPRISES TREATING SAID STRUCTURES WITH AN AQUEOUS DYE BATH CONTAINING 1% TO 5% BY WEIGHT OF THE BATH OF META-CRESOL AND A DISPERSED ACETATE DYE. 